3.3 Soil Systems - F.P.W. Winteringham

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3.3
Soil Systems
F. P. W. Wll>TEIIJl<GHA\\'
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3.3.\
3.3.2
3.3.3
3,3,32
3.3.3.3
3.3.3.4
3.3.3.5
3.3.3.6
3.3.4
3.3.S
,m
In'roduction
Principles
3,3,2,1 The soil profile
3.3.2.2 Spalial .. ri.~Ii"
Input.. OriiinJI.nd Path",">,
3.3,3.\ The atmosphere
on
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172
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[rrip'i"" and flood,n,
Af:,ocllemi<lll
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W.,te ""-"}'dini
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p.'h
dol'''''''' dum[>'ni
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Abiotic Di..p'punutC< hCl<ln
3,3.4.1 V"latilization
3.3,4 2 pho,ocllemical decompo.ition
3.3,4.3 Ero<ion and ",n-<lff
3.3.4.4 Luchini
3.3.4.S Abiollc in.eti".,ion in 'ilU
Biotic Di..p'pu,,_ F><1On
33.S,\ Plan"
3.3.5.2 U"e"ock.nd "ildlif.
3.3.S.3 SOli faun••nd no",
3.3,6 Effecti,·. Coneen',,"OnJI
3.].6.\ Con,in""", inpu'
3.3.6.2 D'<e<>n,inuou. inpu'
3.3.6.3 A,·.il.bih')'
3.].7 T..".nd Model,
3,3,7,1 laboratO<)
3.372 Model'
3.3.8 Critic.1 Appro;.. I.nd Re,..."h 1'«<1.
3.3.8.1 Th. co.. ror 1.00<"0<)
33,8.2 Optimal u" of t. .n fo' p.-edktio.
3.3,8.3 R.....-ch nuds
3.3.9 Swnmary and Coucl ..~
3.3 10 Reler.nee,
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170
TEITS TO PREDICT THE ENVIRO~MENTAl BEHAVIOUR OF CHEMICALS
3.3.1 11'I'TRODUcnOS
Soil. are the relativel) thin film of helerogeneou. panieulate and fibrous
matter whieh ronslitute. much of Ihe land·almosphere interface. The) are a
complex mixlure of mineral.. carbonaceous mailer and water. in whieh he
the "a" range of mil.T<Hlrgani.m•. and Ihe soil-fauna and flora. Oa..iflcation
i' tradilionaU) based upon abiol;" composition. origm and geograph)' (Finch
and Trev.'anha. 19J9. PI', J54-466; Ehrlich el al.• 1977. PI'. 254-255). Soils
are a mOSI ,-ilal pari of Ihe human environmenl since they suppon the emire
range of lerremial flora and their directly. or mdirecdy-dependent fauna
including man.
Currenl Irend' in world population. and in food. energ). fibre, and
chemical demand. per head of population, have emphasized the effective I)'
limited nalUre of cultivated and economically culli"able soil. and the urgenl
need to protecl Ihis reSOurce (UNEr, 1977; FAD. 19793; Wimeringham,
1979~ 1980a).
II is now clear Ihal immense, and possibly irreversible. damage to many
soil. of Ihe world has alread)' occurred as a result of human acti"iti" in recent
millennia and e'en in recenl decade<. These aClivilie. include deforestation.
shifting agricultural practices, over-grazing, agricultural intensification.
pollution and especially industrial and urban de'·elopment. Agricultural
intensificalion has in,'oh'ed an increasing energ} input per food calorie
ingested by man, fenilizer and pesticide usage, and anificial irrigation
(Wimeringham.1980a).
This conlribulion COnccrns part of Ihe problem of prolecling soils,
especially agricultural soils, from Ihe undesirable effects of agricultural and
Olher environ menial chemicals which reach Ihe soil. eilher imemionally or
unintenlionally, In panicular, it relates to the use of laboralOf)' or field lests in
order to predici chemical concemration le"els likely 10 be achieved in lhe
parlicular soil system under consideralion,
Simple mndels (see Seclions 3.3.7.1 and 3.3.7.2) playa useful role in the
handling and presenlation of dam On concentratiQ<lS and mOvementS in and
belween the "anous companment. (e.g. plam, Ihe soil profile. drainage
horiwn) of lhe soil eCOS)'Slem, To pro"ide for Ihe great rompl..it) and
variabihty of Ihe soil ecos)'stem in vi"o, Ihe laboraIOf)' delermination of
companlti"e rale COnstanls would appear mOre useful than lhat of absolute
rale con.tant. in isola lion (see Section 3,3.8).
The asseSSment of possible erological hazard or biological impact will. in
tum, depend upon the nature of the crilical chemical-biotic interaction'
wilhin Ihe ecosystem O"'r the same range of chemical concentrations Or
le"el" Ihi. taking into account the relation betwe<:n measured or predicted
concentration and its a"ailability 10 lhe exposed organism.
It is difficult to envisage any simple Or useful model in Ihe 0,·....11
'"
SOILSVSTE.MS
chemical-biological-socio-eoonomic context. The onl)" feasible objecti,'e in
that context would be a balanced judgement based upon the need for food
and other agricultural and fore,try proouCl', re",uree conservation. and
emlogical hazard in that order, The as«ssmenl of biological impaCi is
di"""ssed under the complemental) SCOPE project entitled Eff«u of
Poiluranu at fM Ecosystem u"e/ (Sheehan ef aI., 1984).
The effecti"e chemical concenrration or le"eJ achie"ed "'ill be the net result
of the nature and magnitude of the inputs, and Ihe variom 'disappearance'
factors which tend to remO"e the chemical, I.e. the outputs, The biological
effeCi' of the chemical will al'" depend upon ito vertical di.tribution in the "'~
profile. and upon the spatial variability between the defined profiles OHr ,he
,o'al "'il surface area of the eco>~'stem under consideration.
It i. con"enient to c1assifl and discuss input. according to origin or purpose
as follows:
(a)
Incidentally from the a,mo>phere as intercepted gaseous poIiutant.
(e.g" that of SO, b)" aerial foliage). as pafliculate {all-out Or deposition.
or as di>SQlved chemical in precipitation.
(b) Incidentally from irrigation and flooding
(c) IntentiOnally from agnxhemical usage. waste reoycling. or from
non·agricultural dumping.
It is con'-enient 10 classify and diSC\l5S outputs as follows,
Abiotic (acton such as ,'olatih~ation from Ihe soil surface, k>s> through
surface soil ero>ion and run-off. down""ard leaching and abiotic
inaCli"ation in Situ.
(b) Biotic factors such a. plant uptake and metaboli.m, grazing animal
absorption and ingestion. bioa<:cumulation and metaboli,m b)' soil
organISm•.
(a)
The .'arious inputs. outputs and the net cons.equence of their integra60n are
discussed seriatim in the follo"'ng $tttiOns.
3.3.2 PKINCIPLl!.S
Soil. are almo>t invariably covered by nalive or cultIVated flora Therefore. it
would be neither useful. nOr at all rulistic. to consider soil in abiotic iSOlation,
only as part of the soil (and i" biota)-piam-atmo>phere 'y>tem. This is
particularll germane to the problem of environmental chemical residues
because their quanti\l,i.. and qualitative fate is mainl)' determined b)'
chemical-biotic interaetion., MO>t important afe plant uptake and
metabolism, and soil microbiological degradation (Kokke and Wintuingham.
1980; Tabak. Qu",'e. Mashni. and Barth in AOAC, 1981. pp. 267-327; see
also Klein and Scheunert. Chapter 4,1; Cabridenc. Chapter 4.2 and Moriarty.
Cbapter 4.5).
I 72
3,3.U
T"ESP.; TO PREDICT mE E.~'VrRO~.'tL~TAL
T~
BE>!'"VIOUR OF OlEMlCALS
Soil Profile
For the purpose of study' or modelling it is usual 10 conSIder a .'ertical element
of 'he soil-plan,-a'mosphere sy,tem represented. or simulaled
experimentally, b) a 'I)",;meler'. The II'Slmeter is a laboratOl} oolumn of
TepTe"'nta,i.'e .oil Or protected monoli'h of undisturbed field soil pro.ided
wilh lacililies for sampling and for monitoring the behaviour of "ater and
,pedfic chemicals, A .'enical diametric (ns) =tion of the soil ooIumn "ill
expose the various lay'ers Or horizons of the soil and the "ertical struaural
.'ariabili'y-i.e .. the soil profile, Lateral dimensions of the Iysimeter .'ary
fTom the few square centimetr.. of a laborato!) column to square melres of
the field II'Simeter, Depth of the IYSlmeter extends '0 some arbitra!)' Or
'cri,ical' limi'. The critical limit may be that below which an en.'ironmental
chemical win cea", '0 inteTaa with the plan'-roo, sl'Slem, Alterna,ivell'. it
may be the effe<:ti.'e drainage horizon or ground "'aler table which. when
reached by a leaching chemical, COUld pose a "'aler pollulion problem,
While a Iysimeter or itS determlni,'ic model can reasonably repre",nlthe
soil profile in deplh at a particular point. il may, by no means. take into
account the spatial .'ariability across the heetare' 01 a natura!. or
artificially·sustained. agricultural ecos)'stem,
3.3.2.2 Spatial Variability
Biggar and Green"'OOd (1978) have discussed and illustraled the nalure and
magnitude of bolb the lateral and .'ertical .'ariabilily of field soils "'ith
particular reference to soil nitrogen and organic matter rontent,
·Macro··lateral \-anabilitl' was expressed as the estimated coefficients of
"ariation in defined parameters when repre",nlath'ely ,""",pled as unit areas
(e.g. I m') ","'er some limited la'eral area (e,g. 100 m,).
Nitrate. lor example. can uodergo denitrification at anaerobic ·micro··sites
whIle. ",'erall. the "'il i' adequalell aeraled and denitrification would not
otherwise be expected to OCCUr. Thi' 'micro' -.'ariabilitl' in"okes dimensions 01
the soil particulate. (i.e. in mm or pm). Obse"'ations. with experimental
Il".imeter, mull largely ignore such micrD-vanabilitl" but ii' existence can
aCCOUnt lor chemical cbange. not otherwi'" indicated by the usual parameters
(e,g. pH. redox potential).
For pur'j)OSt$ of prediction On tlie ecos)'stem ....Ie On the basi. of Il'simeter
studies it will. dearll. be most important to take Into accoun, the spatial
variability and "'il surface topography in fact.
I'iel",n~r ai, (19g0a; b) ha"e developed a ·....Iing· method to quantity and
allow lor the spatial "anability of field soils, They have succ:essfull)' applied it
to the p~diction of the cumulative leaching of NO, on tbe hectare scale,
'Their method takes into account both spatial and lemporal variability of the
soil. "'aler status. samplt si~e, et~, Predit;tion of cumulative leaching on a
stochastic basi' could then be made quan,itati,'ely
m
SOILS~STE.\IS
3.3.3
I~PlJfS,
OIUGIJIoS AJIoO PATHWAYS
3.3.3.1 TM At"""",""re
Soil can be ad'ersel) affecled b) atmospheric·borne conlaminant> such as
sulphur dioxide. parliculale loxic metals (Cu, Zn, Pb), or acid rain (NO,..
SO,' , SO.' ). Radioactive substance. can also 'oach lhe soil lhrough
atmospheric faU..,.,.t, Ho",e..er. for ,'ari<>us ,raSOnS discussed el..... here
(FAO/UNEP, 1977) it i. improbable that the soil eC(5)"1trm "'ould be
significanll) damaged rtF" ,,'ilhoul sinlUltaneou.lj in"ol"ing all Ihe alarms
and countermeasure. for the radiological proleetion of man, Atmospheric
fall-out and precipitation rrprrsent an area SOurce of environmental
chemical. while atmospheric lead contaminalion from a bu') moto""a) would
be a line souree.
Sulphu, and nitrogen o.i~ from indullrial area and point sources are the
most serious atmospheric pollutant. of soil. Thi. i. due 10 the etfec15 of acid
precipllation on soil pH. and Ihe resulling Increased leaching of soil nulnenlS.
The imporlant prognostic indicators in Ihis conlext are pH of the
prrcipiiation, buffering capacil) and a,'ailable mineral rontrni of lhe soil. and
" ..ter infdtration (Maimer, 1916; Glass ( l aJ .. 1919),
3.3.3.2
Irrigation and I'IoodIng
TIle use of unsuitable "'aler for agricultural irnga\lon OT flooding can lead 10
SQiI pollutIon, 10 unarceptable levels of nilrogen, phosphoru., sodium,
chloride, pH, etc, Guidelines are ",'ail.ble for tlie testing of "'aler suilabihl)
for agricullurr (A)'ers and We.tCOt, 1916), Flooding usually originat.. from a
line source (e.g. from a bursl ri, er bank). Extensive flooding Wilh saline water
from the sea. a. with certain kinds of ""Ste dumping and accidenlal rrleasrs
(see below), presents problems of reclamation ratl>er than of prediction, The
reclamation of saline soils ha' been extensi'ely studied and ,uccessfuU~
undenaken in huge area. of the "etherlands (Glopper and Smits, 1914).
3.3.3.3 Agrochemlral Usage
beessi"e or unsuitable application. of pe<ticides, fertilizen, gl'O"1h
regulators, ha",'est·aid chemicals. etc. can ob\iously load'to undeSirable
residue. in sod and in ha", ..ted crops, or lead to ground " ..ter pollution
(especially b) nilrate.) and pollution of surf= waters exposed to eroded soil
(e,g, with peslicides). This subjecl has been e..en,i,e1l discussed and
revie",ed elsewhere (e.g., USDAjEPA, 1975; FAO/UNEP, 1976;
FAO/UNEP, 1977; FAO.1979b; Kornberg. 1979).
Unlike environmental chemicals which reach the agro.eC05~'S1em in
precipitation or through S)"1tematic irrigation, agrochemical, are usually
applied sporadically (e.g, for pe.t control) Or infrequentl)' even though
174
IF.sTIiTO PREDICI THE I;NVIRO"ME"TAL BEH"VIOUR OFCHEMI0'lLS
regularl) (q.
a~ an annuall~rtilil:cr
appliWlion). The
fonn~f r~prcsem
more
Ihe conditions of a 'continuou~ inpur" while 'he laueT repreS"n' 'h"", of a
'di>ronlinuous inpu,' (S"e Seclion 3.3,6).
3.3.3.4 Waste Reqding
The uS" of municipal sludge as ferlilizers can lead 10 soil pollutiOn wjlh toxic
metals suCh as lead. line. copper. cadmium and mercury (Bryce.Smilh, 1973;
Kurihara, 1978). Similarly'. the applica,ion of organic wasteS geneTated by
intensive hestock fanning can lead to ncessi'e residue. in "'il of "arious
minerals including I'H;, NO, and toxic metal. (Conenie and Van de Maele,
1974; Vie". 1974), 11 is clearly better 10 determine potentially unde'irabie
residue, by ,ludge or animal w'a"e analy,is before application 10 the ",il
(Baker and Che~nin. 1975).
3.3.3.5 Waste o..lIOSits, [lumping
The dumping of municipal. indumial or mining w"Sles can represenl "'rious
poin, or area lOurees of lOil poilu' ion according to Ihe >cale of deposil.
Dumping rna)' be uncomrolled or e'-en undelected al the time 10 Ihal lhe
nalure and magnilude of lhe pollulion problem cannol be predicted. Olher
form, such as municipal wasle deposits and mining w"ste. are ",ually
controlled and lhe nalure of the hazard '0 Ihe """ered or ncighbounng ",ils
well recognized.
Thus, again. il is mOle a problem of e,'entual ",il re<'lamalion than of
prediclion. The redama'ion of soil. polluted by ,'ariou. induslrial w-asles has
been nlens",'ely studied, e.g. Ihe redamalion of land u!oed for COllI·mining by
the eXlensi.. 'spod dumps' w'hich comain higJt proportion, of FeS,
(Doubleday, 1974). Soil pollulion can occur a. a re~ull of an a""idem, e,g..
the highway spillage of a lOxic chemical (Kornberg, 1979). aearly. the
conlrol of .uch point lOuree, i, laTgely a maner of educalion, legislation and
redamalion. Such accidenlal relea"'s can only be predicted al large on a
purely stochaSlic basi•. They have, however, pr""ided unique oppoTlunilie,
lor studying Iransport ollhe chemical. Ie' ell, biological effe<'l$, ele., but only'
af'er Ihe e,-ent. for uample, Ih"'" follo,,'ing Ihe accidemal relea", of
2.3,7.g.letrachloro-dibenzo-p-dioxln (TCDD) at $eve", in hall' and Ihe
appearan~ of residues in local ",ii, (WHO, 1977; Pocchiari tl aI., 1980)
3.3.3.6 Path..a).
Ha,'ing reached lhe lOil. em'ironmental chemical. can be ITanSjlOl1ed laterally
by surface erosion cau",d by' wind, or by surface w'aler drainage from sloping
soils. They can m<We ,'uhcally in,o Ihe atmosphere b)' "olatiliUl1ion
SOIL SYSTE.'.\S
processes. or down the soil profile bj leaching. In addition they can undergo
chcmical lf1lnsl'ormations and redistribution ";thin lhe soil_plant_
atmosphere system as a ",suit of chemical_bIotIc interaction•. and bj gaseous
or solule diffusion. Manj simple and elaborale models for these processes
hav'e been described (e,g.. bj Frissel. 1977: Dragsan and Giddings. 1978).
A great deal of current intelligence on the path"'a)-s of ehemical elements
in the !.Oil-plant-atmosphere system is owing to the v'ery utensiv'e
quantitativ'e studies of radionuclides in the env'ironment following lheir
release from point, line or area SOUrces (e·8·. see CEC. 1972).
3.3.4 ARIQnc OISAPPEARAJIoCE FACTORS
3.3.4.1 Volatilizati...,
This is a major palhway by "'!iich some environmental chemicals can be losl
from the soil surface. for example, NO,·N as N, and :",0 as a result of
anaerobic denitrification in lemporarilj nooded soil•. or a•• olatile amine.
and NH, from animal "'aste,
The loss of pesticide residue, by' "olati\ization processe. ha' been ,,-.11
studied. Volatiliution rates from planl or moist soil surfaces can be .'ery
large. with losses approaching 90~ within 3 da)'s for more volatile
compounds. Losses from dry' soil are much Jess. Strong adsorption of
pesticides by the dry soil greatl)' lo"'e" Ihe "apor pressure to a le"el so that
,'oJatihUl\ion from exposed dry' surfaces is almosl entirely Inhibited (Tajlor.
1978).
Taylor (197g) has also presented ,imple equations for the .'enicol nux of
pestiCIde from soil or leaf surfaces as a funnion of concentralion gradient.
turbulent air now, elc,. and illumated volatilization rates as a function of
equilibrium vapor pressure for v'arious pesticides,
The use of radio-isotopically labelled compound, applied to test sods under
defined conditions has one unique ad.'antage when quantifying .-olatiliution.
or indeed anj' other disappeaf1lnce faetor. on the basis of a 'balance' study'. It
pro"ides for the easy detenion of 'bound residues' ,,'hich might not be
recovered b)' ron.'entional chemical ..Iraction (FAO/lAEA. 198OC. p. 291).
A modification of the laboralOl) Sy-S1em described by' Ebing and Schuphan
(1979) would lend itself ""ell 10 such balance ~ludi~ "';th lhe
soil-planl_atmosphere Sj-Slem.
3.3.4.2 Pbotodlftnlcal OrromPll"lt1on
The method described by Kone el al. (1978) dearl} pr""ide. a useful
indicator of romparative photochemical decomposition rales. Here. the leSt
176
TESfS m PREDICT TIlE. E..'<V1RO"ME..',.AI- BEllAvlOUR OF CHLMICAI.S
''Clabelled compound is adsorbed On an inen particulate and eXpoloCd to a
mercury lamp. decomposition being aS5oll)ed as "CO,.
3.3.4,3 El"Osloo and Run-off
!;e"eral empirical equations describe surface soil erosion and 'run-off' as a
funclion of ....ind. precipitation. soil t)'l"'. slope. etc.. e,g.. the Uni"ersal Soil
Loss Equation (USLE) used by the Unite<! States Dep.artmem of Agricultuu
(USDA/EPA. 1975. pp. 16-21), The rate of 105$ of an em'i,onmental
chemical On this basis "'ill then be the product of erosion r.le (e,g .. as kg soil
h. l )'r ') and concentr.t,on of en,'ironmema] ehemical in the rele ..nttop
la)er of soil. Such losses cannot be reli'bly pre<!ine<! o,'e, short period.
beamse of the "iciS$,tudes of dimate, wind force, "';nd direction.
precipil.tion. etc. upon all of ",nich the erosion mUSI depend
),I.ny equ.tions and models h"'e been designed to represent the physical
mo"ement of en,ironmemal chemicals both up and do"'I'l the soil profile
according to precipitation. soil .....ter status. evapotranspiration. etc. (Enfield
.nd Carsel in AOAC, 1991, pp. ;233-;250), Reference has been made to
many of the equations and models by Da)'ananda e' al. (19g0) and by
Winteringham (I980b) ",ho have alw described rel.t",ely simple equations
for predicting comparati"e leaching r.tes (and implied losses to the root zone)
of wlutes under a .ucceS$ion of precipitation and drying e"enlS, Helling and
Draggan ha"e discussed the problems of predict,ng le.ching r.tes on the basis
of laboratOly tests for organic compounds (AOAC. 198\, pp ~3-88)
In addition to the fOregoing abtot;c remo,.1 mechanisms a cltemical residue
m.y be effecti\ely remo..d in the ecotoxicological context either by simple
chemical decompositiOl1 in si,u (e,g, the abiotic degradation of .trazine
residues in wil '" ,eported by Skipper er al .. 1967) and/or b} >Irong
adsorption On the particulate 0' interparticula,e surface (e.g. 'he
ton-exehange ty pe adsorption of bipyridylium herbicid~ residues expl.ined by
Calderbank. 1968), Total and abiotic ,emo,'al arc usuall)' differentiated b)'
th~ effect' of soil sterilization on the observed di<appearanee rate.
3.3.5 BIOTIC D1S,\.PPEAIlA,"CE FACTORS
3.3.5.1 Planlll
There is a \'et)' ~"en,i,'~ lilCratu,~ on experiment' .nd models for the uptale
and metabolism of nutrients and en,'ironment.1 chemical residue, by plan\!
m
sorl SYSTEMS
from th~ soil and rhe crilical imponance of e~aporranspiralionof warer in Ihis
COntexl (see FAO/UNEP. 1977). Data are also a,aiJabl~ on ner removal a. a
resull of harvesi. grazing. ~I~, (se~ Fnssel. 1977).
3.3.5.2 LheMock and \\1ldUfe
Wh~e man)" studies ha"e be~n made On Ih~ metabohsm and effeel of
environmental ~hemicals. especiaUI of pesticides. on laboralory and farm
animals and upon w~dlif~ specie, (e,g. see Pimenlel. 1971). no significant
information Or data w~re found on rhe reoprQCaI ~ffects on soil
concentralions of otherwise un.,opulated land, Such effects would. ho"'·C'er.
be expected 10 be small and. in any e,enl, depend fi,.dl u.,on plant uprah
from Ihe soil and significant accumulation in the edible p"rtS of the aerial plan!.
3.3.5.3 Soil Fauna and Flora
There is abundant e,'id~nce that bj. Ihe proce"". of bioaceumulation and
biodegradation Ihe soil fauna and flora (including microbiological acrion)
represent an imponant faelor in rhe disappearance of many organic chemical
residues from Ihe soil (e.pecialll under anaerobic condirions) or aquatic
en,ironm~nt (Draggan and Giddings. 1978; Kokke and Wintenngham. 1980;
£1 Beilt1 at .. 1981; see also Cabridenc. chapter 4.2), thiS despile One cunous
and surprising conclusion 10 rhe conltary (l>loriarr}, 1978. p. 116). Many
models and melhod' are a.-aiJable for quantifying a[)sorplion,
bioaceumulation. in8e"ion. degradation and melabolism, ~Ic. by soil
mIcroorganIsms and other soil biora (see FAOiUNEP. 1977),
\Iicrobiological aeli'iry can I~ad to Ihe formation of rdali,'dl' polar
melaboliles which may then be lost by leaching (especially as NO,) Or to
relati"ely 'olalile products "'hich ma} th~n be 100t from th~ soil surface: (as
S-compoonds. NH,. 1\,0. !\,. etc.). Alternari"I}. residues can become
m~tabolize<.l and Morcd in the organic matter pool of Ihe soil il""lf.
J.J.' EFFECTln: COSCE","RATlO"'S
en,ironm~ntal ch~micallnto the soil
would be strictly continuou, (d, Butler. 1978), It is likely to reach Ihe soil a, a
series of r~gular or sporadic pul"",. for example. as a resull of agrochemical
applications, Ho""e"r. it i' useful to compare the >oil residues respec'i,dl'
resulting from a hypothetical continuous exposure and a di=ntinuous bu'
lOtal dose-equivalent one. other things being equal.
It is unlilely Ihallhe rale of input of any
3.3.'.1
Contlnu~ Input
Thi' condilion mighl be appro'imaled b}' a soil exposed 10 fa\loOut from S(lme
ul'""';nd indu'trial complex. or 10 Ihe relati,'el) ",gular Input> as a result of
178
TESTS TO PREOtCf THE E."VtRO~J,tE""TAl BEHAVtOUR OF CHE.'llCALS
<.!ail) irrigatiO~ "ilh poor qua~ly water. a situation by no mean. unu.ual
during 1he long growing ~asons of arid·zone agriculture_
Let the soil receive the chcmical al a conSlanl ,npul ralC. t, units of soil
o:mcentration equi>'alent per unit of time (e.g.. kg chemical, per
hectare--<:lepth of lhe rhiz",phere. per lear). Since Ihe concenltalion of
environmenlai Chemical is likely to bt' '-ef)' low it is rfcaso~able to expeclthal
lhe overall di~ppearance (in Ihe ab>oence of abrupt ccssalion of inpul) would
bt' exponential "ilh lime (Winteringham. 1971), In the ca~ of enzymic
degradation this would. indeed, be expected from classical Michaelis-Menten
em)me kinetics as demonSlrRled for acel~'lcholine eslerase acti"ilY al "et)
10'" subslrale concentralion•. Here, lhe disappearance rale constant was
V/Km, u.ing lhe conventional s)'mbo1l of en2)'me kinetics (Winteringham
and Disney. 1964: Winteringham and Fowler. 1%6). Lellhe disappearance
rale conStant A(in appropriale uni", e_g. years' a. above) Wilh respect 10 Ihe
rhi,,,,phere unde' consideration (~e abo'e) be Ihe addili"e resuh of the
separale disappearance faelors such a. microbiological degradation.
"olatHization, leaching. etc. This addili"e rale i. analogou. 10 the effective
disappearance rale COnSlant for the specific radionuclide burden of an ammal
due 10 the combined effeclS of excrelion and radioaclive decal' (e.g.. $Ce
ICRP, 1960, pp, 33-34),
Thus. when lhe soil concenlralion is C; at an) tnSlant:
dC/dT· t - AC
(>,
Assuming C - C - 0 ,,'hen T - O. 1M =nlralion C, achie'ed afler time
T "ill be gi"en by:
C, - J{I - e "}'A
("
\',lIen T is large compared "'ilh lhe o"erall disappearance half-time
(T, , _ 0.693150), a sleady'-slate concentralion, C" "ill be achie, ed SO lhal:
C,-fIA-C
("
Then C, will also lend 10 become identical with the lime_weighted mean
concentralion, C, "' also indicated in equalion (3).
If the inpu.. cease (e.g, lI> a re\uh of a control meaSUre Or change in
agricuhural praCtice), the residue "'ill disappear cxponentially with time so
lhale
dC/dT· -K
and C" - C,e "
(4)
where T is now the time after 'lopping the input "hen the concentration had
'eached the ,·alue C, (and ...·hieh mighl already be CJ. The
time---roncentration curye under all lhe..e condilions i. illustrated in Figure
3.3.1.
",
SOIL SYSTEMS
..
-----:-,-,-,-O-"-"------,~ ,c
,
C, fl,-,·")/'
_ , ~"'1,C•• C " f " . t
Figure 3.3,] Nature <>f tIM: timc:-<XlrIC<Ontration
curve under ""ndiu"". of ""nUn""'" ;nl"'t (_
Seeri"" 3,3,6,1), Contmuon. ;npnt (/)'Enceri,c
.. ponent;al d;..WC.ua1lO< ro,c constant A, cor,c.·
pond'ng half-'ime t"
3.3.6.2 DisronlinllOUS lnpm
Thi. condition "'ould be repre",nted by an annual herbicide app~cation
when lhe total disappearance half·time T", i. not negligibl)' omali ""mpared
wilh the lime interval. t. belween each application or pul",. i,e, Ihe time
"'eighled mean concentralion "'illlend 10 increa'" "'ilh succcs.si"e pul",s unlil
SOme Slead}' slate belween inpul' and dioal'P"arance oblains.
For comparison with the ,,",'" of conlinuou~ ,npUI (soe abo"e), il i5 assumed
lhal onl) lhe pallern of input is now altered. i.e. when C. is lhe instant
afle, "
concenlration e'lui"alen' of lhe Ii"l pul>< I _ Colt. and T _
succcs.si,·e applicalions. It can be .hown Ihat:
n'
C. -
C._,· e-" + C,
",
T"" il can be sho"'n lhal C. will reach a Slead),-Stale peak "alue C,
When
such lhat;
C.-C,-CJ(/-9)
"j
and lhe lime-weighled mean concentralion C, "ill now be:
C,-~'
CJ(I- 6) - ~·C.
p,
The conslant 6 (0 < 9 < 1) '5 lhe re.idue remaining al lhe end of any lim.
inlerval. '. bUI al lhe instant preceding lhe ""xl pul",. and ..pressed os a
fraction of lhe peak residue aeh;e,'~ in adding lhelos! pul",. Le, 9 _ e ".
180
TESTS TO PR,EOICJTIiE ESVIR.OJ<,"EJ<,TAL BEHAVIOUR, OFCHE"ICAL>
The COO'lanl .p (0 < <J> < I) is $imilarl~ the lime weighted mean ooncen·
tr3.l;0ll over the time interval, " also e~pres.sed as a fraetion of the peak
concenlration at the beginning of the intel'\'al. It follows that:
.
,,{'e'··dI-C/C
..
<J>-~
(8)
C. is Ihe lime-"'eighted mean concentration o"er Ihe time interval' and C.
the initial peak concentrallon on adding the (n + ljth pulse. h ,hould be
noted that ¢> and 9 are COnStantS determined only 1»' 1 and I. The
time-concentration CU,,'e under these conditions of discontinuous input is
iIlu<trated in Figure 3.3.2,
These considerations haH tWo important implications:
(a) Initial peak eot>eentraliOllS under the conditions of discontinuous inpul
can greatly exceed the maxima achie'ed ""ith eontinuou, input. More
serious acute 1O,1c effeCIS on soil biota "'ould, therefore, be e.pected
from a discontinuou, input
(b) (h'er relati"elj long periods of lime (T ~ 1 or T",) the time·""eighted
mean concentrations lend to the same value whether input is continuous
oe,
~r,->.C
,
T I_ '" I
Figu ... 3.3.2 'atu... of tbe time-<X>n<:Cntration OlII'\'e
under oonditioll< or di>rontinuou$ Of ·pul..d' input
Mean ra", of .npnt aOO of di..ppca..""" rote """'tant
a....med to be i""ntical "'ith conditions of rontinuous
,nput illustrated in Figure 3.3.t (..e SoCIi"" 3.3.6.2)
T ~ -
DOC<HumlW«> input [I ~
C""l
C•• ,~C.'e·+C(
..benT. IC• • C,· CollI - 8)ande - .cJ(l - 4t)
",here .. and 8 a ... """,,ant< rOT gi>'en ,.lues of J and,
SOil SYSTEMS
'"
or di<eonlinuou., Therefore, 'dose commitments' (5« BUller, 1978) for
exposed populations ,.-ould also lend to equalize TItuS, long term effe<:t,
such a, the accumulated upta.. from the soil b) ,.-oody perennials "'ould
likewise tend to be independent of the pallern of input (other things
be,ng equal)
Long term effects of different application regime.. sum as the emergence of a
toxic chemical·resistant populallon of arthropods or microorganisms ,,'hich
invoh'es both acute lethal action and long term population selection. could
not usefuUI be predicted in the current OIate of kno,.-Iedge
3,3,6,3 Mailability
It is important to diStinguish bet"'een the total prt<:lictt<:l or determined
concentration of an environmental chemical in the soit and the fraction
thereof which is mobile Or biologicall} acti,·e. Thu.. certain elements mal be
prescnt in soil at concentrations in the range of 10' to 10' p_p.mo> but the
ptant_a,'ailable or mobile fractions may lie only "ithin the 1-10 p.p.m. range
(Profe""r Andr~ Cottenie, personal communication, 1977), Simdarl~',
studies ha"e shown thai onl}' relatively small fraclion' of otherwise 10xic
le,-el. of arsenic or meKllTj in Ihe sod are a>-ailable for plant uptake or
Icach,ng (Stewart'" tJi., (975).
A"ailabiJjt~ can be classified On the basis of e.tractabilit~' ...ith neulral and
,ncrea'ingl)' acid solHntS-that with strong acids often being used to
determine the total soil pool (Viets, 19(2),
It is. similarly, imporUlnt to recognile that llie une'tractable or 'bound'
fraction of a chemical residue in soil may in fact be biologically ",'adable or
acti ... Thus, Fuhremann and Lichtenste;n (l97g) have shown that some
'bound' pesticide ,..,sidues in soil can appa,..,ntl~' be taken up by plants and
earthworms (sce also Chapter 4.5)_ Ho"e>'er, "' wamed c1sewhe,..,
(Wintenngham, 1972). the appearance of an isotopic label in SOme
wmpartment of an ccos)'l1em initially e.posed to an added labelled
en>'ironmenUlI chemical does nOt necessaril) indicate the p",scnce of a
significant metabolite Or den,"ti"e of the onginal compound. Like...'isc, a
met.bol;te or chemical decomposi,ion product ;s nOt n..essaril)' Without
cc-otoxi""logical significance (Winteringham, 1977; EI Beit el al .. 1981).
A, ,.-ith plant nulrients, a"ailability and potential for biolog;cal interaction
will depend upon the chemistTj' of the residue ~r ~ .. "'ell as upon the
physical--chemical water S1aUl. of the soil. The careful usc of isolopic dilution
and tracer te<:hniques for estimating a"ailability. biooccumulation, etc. is well
eSlabli,ht<:l (e,g. see Fried and Br~shan. 1967, pp, 182-219; IAEA, 1976.
pp, 43-46), The use of radio-isotopically labelled compounds pr(>\-'ide, a
unique method lor the detection of 'bound' residue> ....hich might not be
182
TESTS TO PREOICT Tl<E El,<VtRO:,<MEl'oTAL BEHA VtOUR OF atE~lICAt.S
rero'ere<! b)' ron'entional ~h~mi~al anaJ~'~I~; but caution muSt al"'3)'$ be
expre"",d in the interpretation of the isotopi~ data (Winteringham. 1972;
FAO/IAEA. 198Oc. p, 291),
3,3.7 TESTS A1''O MODELS
Against the above l>ackground the problem of predicting the behaviour of an
en"ironmental chemical in the soil_plant_almosphere s)'<tem can be
described in term, of specifIC information and data requirements. These are,
essentially,
(a) Identif}'ing the significam parameters 01 the soil-plant 'ystem in terms of
Ooral CO'o'er, soil. agricultural and irrigatiOn practice. if relevant. climate,
e"apotranspiration rales. precipilation and/or irrigation practice.
juxlaposition in relation 10 possible unimended poinl, line Or area
source. of environmental chemicals.
(b) Ouamif)'ing the existing Or likely input rale (I) of the equalions explained
in Seetion~ 3.3.6.1 or 3.3.6.2 Or their mOre sophiSTicated relall"es,
(e) Quanlif}'ing the separale and deri"ed ""erall disappearance rale constant
(1) of the same equation. Or their mOre sophisti~aled relalive•. Solving
the e<juations for !he le.1 compound and comparing the results ",'ilh lhose
for one or more reference dlemicals "'hOSfc behaviour and biological
.ignificance in the soil_plant_atmosphere «»sy.tem ha,'e been
extensively studied (e.g. the classical peslicides, radionuclides, toxic
elements, ferrilizers. industrial pollutant., et~,).
The .imple equations of Section. 3,3.6, I and 3.3,6.2 al least provide some
rational basi. for the lime_soil concentration curve and its limiting
paramelers (stead)' ,tate maxima. time-"'eighted mean', etc.). H"",'e"er, they
provide no information on the distribution of the chemical be,ween t....o or
more of the virtually unlimited theorelical compartments ollhe soil_planl
system ;n vivo. Such companments would include the har'ested Or edible
pan. of a crop. the crop root zone. leachate or drainage water. surface
run-off. etc.
II i. the puTpOSC of the experimental laboratory or mathematical model to
simulate these more complex systems. An)' review of this rapid!)' expanding
.ubje~, which nOW invol"e' ,}',tem. anal}',i. and computer-aided modelling i'
oUlside the scope of lhis monograph. Instead some represenlati"e tests and
models will be used as a basi. for an overall critical appraisal.
3.3.7.1 LaboralO<}' Tosts
A coUection or ·protocol' of recom.mende<! or <landardized teSlS will not here
be deemed a model (see Section 3.3.7,2) unless the te,lS can be linked
SOlLSYSTB1S
>8,
explicitly '0 indieale compartmenlal distribution or Irander rales within the
simulated ecosySlem.
Meeting the re<jUiremenl' of (a), abo'-e, clearl)' invoh'e$ observal;on and
colle<:tioo of exisling information and data. For (b) adequate data may also be
a"ailable, This aspeet is then Ihe subjecl of 'Slali'ti", and nOt of experimenlal
in"esligation' (Korte el 1>1., 1978. p.80). The ex"ling or recommended
herbicide or fertilizer applicalion raleS for an agriwltural crop aTe lhe 00' ious
example.
In !<lme caseS da.. on effeclive inpuls will depend, al least in part. upotl
laboralOr} and field leStS, for example. in Ihe ca>c of a known agricullural
irrigalion regime bur wilh "-ate< of unknown qualilj'. Chemical and biological
anal)";s of Ihe waler will be ,,"hcaled. Similarlj'. ",here atmospberic fall-<>u1 is
,ugge'ted by agricultural or otber land area-induslrial juxlapoosili<m, air
sampling and analysi, maj' be indicated_ Soil inpul can Ihen be eslimaled on the
basis of ,",'ell known deposilion Sludie, (Whelpdale. 1974; Schwela. 1979).
Most leSI prOlocols felale 10 disappearan« facton (c) abo,'e. U,ually Ihey
relare also 10 specific abIotic condiuon. and onlj to one or lwo biological
species ,,-hieh, hopefull}'. "'ill al least be rele,-ant to Ihe soil <'OO<y.tem under
,.;>nSlderatiOll. Many le$IS have been standardized for official nali<mal or
internation.1 use, e.g" by CEC and OECD counlries (Gilbert, 1979; Smeers,
1979), While biodegradabilily of a compound i. inevilablj' lesl.•peciflC, there
is often reasonable agr..,ment bel"'·..,n the vari"'" tesls ",'ben u>cd to compare a range of different compounds. for e.. mple. in tesls designed 10 .imu·
laIc sewage Irealment and "'1Iter purificalion (Gerike and Fis<:her. 1979). The
real value of iaboralory le't'. therefore, .ppe.lS 10 lie in Ihe e"alualion of
comporali\C properlie. of en"ironmental chemieals. h is Ihes<: comparative
data ""hleh provide lhe mosl reliable basis for Ibe predietion of behaviour in
Ihe eCOSj'Slem in "iV<>, AI.....). provided rhar SOme actual field dala on le,'el,
and effeet' of.1 leasl one of the lesled chemieals are available.
The biochemiStry and toxicolog) of xenobiol;" are remarkabl~ constant at
the molecular le'-el. species notwilb'tanding, For eumple. bolb toxieit), and
mecbani,ms of act;on of insecticides al Ihe mole<:ular or cellular le'-el
"-ere found 10 be .urprisl1lglj "milar for both Insecta and mammalia
(...."1nlenngbam and Barnes. 1955; Winleringham. 1957; 1965). Moreo'cr.
wilhin homologous serie, of cbemical compounds. or wilhin analogues and
SllUcturallj'.relaled groups. there is often a well-defined correlalion belween
chemical ,truclure and biological activil)' (e.g.. see Ferguson. 1939; Sexton,
1%3)
Man~' laboralOr} leslS (e,g. oil-wale< partilioning) for evalualing abiotic
disappearance rales .ucb as ,hose due to leaching also provide reliable data
on compoTal;"e beha"iour in the '-ery much more complex coosystem. Thus.
the oetanol-"'aler parlilion coefficient can usefuUy indicate relati"e
184
TESTS TO PREDICT THE E."VIRO"~lD"T AL BEHAVIOUR Of CHE'-tICALS
mobililie. in ..,il (Briggs, 1977 as quoted in Winterin~am, 198Ob; Helling
and Dragun in AOAC, 1981, pp. 43-88).
Thu" Ihe u.., of suitable laborato!) lests to indicate Ihe comparali,'e
beha,iour of different chemicaJs in the soil-plant ecosystem e"identl} has
a sound basis, \loreo'er, it has the ad"antage. of anticipating possible
ecological haz.a.rds and ob"iating the need for premalure trials or relea.."
which in"ol"e chemical contamination of the eoos}otem,
Draggan and Giddings (1978) ha"e u..,full} discussed the range of laborat·
ory lest, for predieting chemical b<ehaviour in both teHe,lrial and aqualic
ecosyStems. Transport between sy·stems through Ihe commOll atmosphere by
"olatilization, deposition. erosion, and itrigalion was also discussed. The tests
re"iewed included'
(a) Batch equilibrium sludies in which Ihe teS' chemit31 is partitioned be·
tween the solid and aqueous phases of a soil_"'''ter mixture;
(b) Leaching of the tesl chemical through a column uniformly packed ...ith
..,il;
(c) Thin layer chroma'ography using soil a. the solid stalionary phase:
(d) Volatility as rate of loss of lhe test chemical from a solution exposed to
controlled air now O'er ,he surfa"C:;
(e) Soil microbiologJcal degradation of Ihe test chemical b}' simple perfusion
of soil in a column ",i'h aeraled. nutrient_fortified solulion of the test
chemical.
A reeenl symposium (AOAC, 1981) resulted in a ..,ries of comprehensj'e
and authoritati'e reports on laboratol)' tests. These included
(a) A comprehen,i"e re' ie...· of Ihe theoretical aspects of I.. aching do"'n Ih..
$Oil profile. and a d"SCription of column and TLC teS'S for e"alualing
comparative leaching rales (Ilelling and Dragun in AOAC, 1981, pp
43-88);
(b) LaboralO!) le," for biod"gradabihty a, applicable to organic poliulantS
assigned prioril} b} the United States En"ironmenlal Protection AVnq
Effluen' Guid..lin..s. The te", im'oh'«I Sta'ic incubation of the 'eSt chern·
ical at two different con"C:ntrations in "'-ater fortified with a yeast extract
and inoculated with a '>tuled' waSle·water input from ....·orking se"'-age
trealment plant. Methods "",re also detailed for emulsify ing hy drophobic
compounds for le,lIng by the same procedure. The general pTOblem of
predicting field biodegradability from laborat<m leSlS "'-as also diswssed
(e,g. Ihe use of closed systems for assessing the biodegradabihly of
volatile organic compound'). The importan"C: of acclimat;zation oflhe
microbial inoculum and in p"".-iding for enzyme induetion during Ihe
test was al$O discus>ed (Tabak, Qua,·e. :-'1ashni and Barth in AOAC,
1981, pp. 267-327).
SOILSYSTE..\\S
'"
The method of ecotoxicological prof~e anal)'sis de'-c1oped b) Korte and his
colleague. (Korte.r al.. 1978; fccitag tr al.. 1979) i' a multite., protocol
designed to prediCithe comparati'-e behaYiour of chemicals under a range of
selected but representati"e condition' of their likely en"ironment, The)
indicate comparative metabolism in mammals (based on tbe rat).
bioaa:umulation in fish (Ltuciscus idllS mela"OlllS). in algae (Chlo'ella fus<:a),
degradation in actiyated sludge under conditions of refuse romposting. and
degradation by incineration and photochemical decomposition (irradiation a'
1> 290 nm).
Sokolo'- (1980) has described a 'stepwise scheme' based mainl) upon
work in the USSR which also pro--'ides for efft<:ts of th• • hemical upon
.nzym. preparations in vitro as w.lI as oth.r chemical-biotic interactions,
3.3.7.2 \Iodels
When mathematical Or .xperim.nlal simulalion take' into account the
Itansf.r and interaClions bet"'·..,n t"'·o Or mOre of th. conceptual Or aClual
compartment. of th. «:OS) Stem in Vivo, Ihe simulation become. a model.
In this cont.xt the simplest model will be the ins'rumented and sampling'
facilitated laboralOT)' Or fi.ld lysim.t.r (see Se.tion 3.3.2,1), It proYides for
disappearance utimates of "olatilit)'. leaching Or drainage m.awr.m.nts.
plant uptake and m.taboli"" and. pos5ibl), for soil microbiological
degradation (e,g. a, used ~- Klein and Kone. 1980). The all-enclosed
soil_plant_atmosphen; S}'St.m r.pr.sents the n.xt St.p in sophisti.ation (e.g
as described b)' Ros••1 al.. 196-t; Ebing and Schuphan. 1979). These models
provide for atmosph.ric sampling and ,h. inr.-oouClion of atmospheric
chemical. as well as for direCl assa) of volatilization and biofixation (e.g. ""ith
''N Or "CO,.labelled atmospheres).
Yet more sophiSticated modelsacc ccpresented by rhat d.scribed by Metcalf
(197~). Here a tank ""as used to house a small ...at.r hod)' ('Iak.') charg.d
with li,-. plankton. mosquito la,,'ae. and fish, The terrestrial "heJr or 'farm'
supported gro"'ing maiz•• etc. The isotopicall).labelied ,est chemical could be
introduced appropriatel)'. for example as an inseClieide spra)'ed on to the
plants. or as a mosqUito larvicide added '0 the water. Distribution.
bioaa:umulation. transfer and degradation in the ,arious compartments of
thi' microcosm could be follo....d.
The ultimate model is, of course. th. use of an actual ecosystem in dvo. for
eoample. the <mall pond a, also used by Klein and Kort. (1980). following
contamination as a result of normal agricultural praClice. an accidental release
or follo,.-ing an intentional addition for th. purpose of the .tud)' (see
Winteringham, 1977 for examples of large·scale field studies), Such studies
rna}' th.n be used as a mod.l for cclat.d «:OS)'5'.m, or for the .. me ecosystem
186
TEST'S TO PREDICT TIlE E.'''V11l0:-'~'E:-'T AL BEHAVIOUIl OF CHEMICALS
in rdaiion to a new environmental chemical evaluated oomparati"ely on the
basis of laboratory testS.
Undoubtedly, some of the mOSt oompre-hensi,'e studies of en"ironmental
chemicals alread) present in various eoos)'stem. are those reported by the
AS>OCIate Comminee on Scientific Criteria for Environmental Ouality
sponsore-d by the National Research Council of Canada (NRCC, 1972 and
later).
3.3.8 CRITICAL APPRAISAL A.'iO R£.';:F.ARCH !"[EOS
3.3.8.1 The Cut for L.bonItory Tosts
Taking also inro aCCOunt rhe discussion of both teslS and models elsewhere
(especially usefully by Dragsan and Giddings, 1978; Cairns. 1979; Giilen in
AOAC. 1981. pp. 214-232; Tabak e,,,I. in AOAC. 1981. pp. 267-327). the
following appraisal is prompted by more than a deeade of intema'ional
eooloxioological re-searcb coordinarion (FAO/tAE-A. 1979; 1980a; b);
Neither teslS nor models can accuratel) represent the Immense oomple,ity
of the soil-plant-atmosphere «OS)~tem in .'i,·o. not to rncntion the infinite
"ariability of chmate and in natural popuiation•. Therefore. the results of leSls
and models should ne"er be assigned lhe precision /IOrmally associated witb
laboratory experiments.
While a field study of a chemically exposed ecos)'stem in
can provide
an aecura.. analysi. of an eootoxioological sl>lem in retrospect. its prognostic
"alue for new chemicals must still be based on comparati"e laborato!)' ,est.
with ,he neW chemicals and well.studied exi,"ng environmental chemicals.
Models and experimental 'microcosms' are useful indicators for chemicals
usigned sufficient priority b)' labora,o,} les, protocol' and can indicate the
potential for intercompartmental transfer. But the COSI. of evalua';on are
likel)' to be higher than the use of laboraro!)' rests and Ihe entire "r"em must
""rely be replaced by fresh abiotic and biotic components after each test.
A major ad"antage of laboratory tests for botb abiotic and biotic--cbemical
interaC1ions is that tbey can be standardized, easily replicated in different
laboratories "..ith different chemicals. and are relali"el) le$$ costl) tban more
sophis1lcated te~t', Moreo"er. the} are mOre oonveniently supe,,'ised by an
uperiene<:d scientist who mlgbt othe,,",'ise have n~i,hu time nor facilitie, for
field vi"ts and remote SUpe"'lSlon. Finall}'....hM a 'Colt merely simulales SOme
of 'he oonditions of the ecos)'stem in I'ivo. it e"idently can provide reliable
oomparati,'e infonnalion w'hich can, indeed. be U.l<'d for prediction On the
ba~;s of referene<: chemicals whose beha"iour in the field has alread) been
"udied
A disadvantage of tbe modei, despite i,s ,uperficial resemblane<: 10
oonditions in the field. is that it can ne"er represent natural populations.
,""0
SOIL SYSTEMS
'"
genetic pools, climate fluctuation. etc. which certainly playa decisive role in
determining the ecological significance 01 an environmental chemical in fact
(see Winterin!/,ham. 1917; 1981). Thus. Frissel (1981) has described no less
than t"-entl differem proposed model5 for the beha"iour of nitrogen in the
soil-plant-atmosphere system but the probtem of identif}'ing the be-st one
remained unsolved!
Since Ihe Cl!oe for predicti"e tests ;5 overwhelming if the possible ecological
h.uards of the e"er VO"'ing range and burden 01 en'ironmental chemicals are
to be amicipated. the e"idence re,'iewed 5uggem that an approach on the
following h~ win be the mOSt useful
3.3.8.2 Optimal Use o/'Tl'SU for Pt'fdiction
The tests 'hould embrace the fun range of parameters limiting or oonUoliing
the beha-'iour of the ehemical in the eCOS}'$tem in addition 10 the ob"ious
physico-<:hemical and biological properties almosl cenain to be availabte.
These would be vapor pres...,re, solub~ity, chemical stab~iry, acute toxicity
to rodents. fish, arthropod,. etc. In addition. the eootoxicological tesl profile
should aim at tUSt to quantify the range of the 'ignificant and, al leasl.
represent..i'·e abiotic and biotic disappearance facton; as outlined in section5
3.3.4 and 3.3.5. Above all these te,ts should be applied comparatively to
include one or more en"ironmental chemicals already widely studied and
documented On account of their past release. usage and presence in actual
ecosystems.
In order to obviate the teSting of an unnecessaril) large number of
substance, and to establish priorities, some preliminary laboralory screening
in,-olving toxicity. chemical and phy.ical properties are clearly indicated.
'Te>! guidelines' and differenl le"el. of .uch teSts ha"e been suggested (van
der Ham elal .. 1981), The concept 01 different le"els or "ages to obviate
unnecessary or premature development has been used for many years in the
WHO testing ~heme for new public heallh insecticides (Wri!/,ht. 1971).
Ha"ini e51ablislted priorities. the need for tests al the microcosm. model or
e"en field le"el can then be oonsidered. Finally, the integrated information is
used for predicting le"el. and peak ooncentrations likely 10 oblain under
practical field condition' bearing in mind the ine'itable limitations of
prediction imposed by spatial. temporal and biological variability of climate.
soil, and natural fluctuation of soil flora and fauna. II i, for Ihe ecolOxicologist
to e"imate or determine the biological significance. if an). of such chemical
concentration, and their time functions.
3.3.8.3 Re.ea"h Nee-ds
At leaSllwo research needs have become evident. Almost all the laboratory
lestS On biOlic interactions are conducted with one or more specifie animal or
188
TESTS TO PREDICT THE E.''''IRO~ 'IE»" AL BEllAVIOUR OF CHE-"IICALS
plant specie" or al be,l, with a relalhel> limited microbiologically acti".
medium. On Ihe OIher hand, Ihere ;,; abundanl ",'idence of Ihe ,'ilal role
play'ed b)'lhe plam root.ystem and the "ast range of soil biota in delermining
Ihe fate and significance of Ihe soil chemical residue, What i. needed Ihen,
appc:an to be a simple laboratory' le,l for al lea'i characlerizing o"erall field
soil biomass and i" aCli'ia. for example on Ihe basi. of ...mpled ATP le'el,.
"CO/CO, respiromell'). elc, (Kokke and Wimeringham. 1980; FAO/IAEA.
198Oc-), Such leStS would complemenl the trophic indices mentioned by
Cairns (1979), They would al least indicate the actual soil potential for
degradation. elC, as indicated by Ihe laboratol')' biodegradation tem in the
preSoCnce of kno".-n biola, They "'ould ol»iate Ihe danger of an apparemly
biodegradable chemical prO\'ing unexpectedly penistent in fact beeauSoC of its
appc:arance in an olherwiSoC unle'led and unusually dry'. low_organic mailer
soil. Such tests hl"e alread)' been de"eloped and widel) u",d for assessing Ihe
comparable net prima')' produClion of aqualic ecosy'stems (IAEA. 1975)
AnOlher imponam but e"idemly negieCled prO\'ision of laborator)' testing
in the p,..SoCm conle~t is Ihal for Ihe ",'en established capacity of inSoCCI'. fungi,
bacleria. plant< (""eeds). and e"en rodents to e"ol"e. O\'er a few generations.
populalions highly resi,tanl 10 an olhe""i'" 10xic chemical such as an
inSoCClicide (Wimering!lam. 1977; 1981).
3.3.9 SUM:'>IARY
A~[) CO~CLUSIO~S
The faClon which determine Ihe beh3"iour of an en"ironmental chemical in
lhe soil profile are described. Simple equalions for predicting concemr:uions
on the basis of known or delermined inpul and disappc:arance rales are gi"en,
La.boralOT)' le,l, and models are briefly reviewed and crilically discussed.
The'" relale mainl) to disappearance factors such as "olaliliZlltion from the
soil surface. loss wilh erosion and run-off. leaching and mobility ,n Ihe soil
profile, and Ihe chemical-biotie interaClions including plant uplake and
melabolism, and microbiological degradalion.
An oplimal usoc of laboralory teSlS and models for the purpose of prediction
i' ,uggested. and the Iimilations imposed b) lemporal and .palial "ariabilit~
of Ihe CCOS)'Slem '!tr....d The ..Iue of comparali"e 1e'l\ing "i1h
well..."ablished en"ironmenlal chemical'! is also "re'SoCd,
Some research needs are ide~lIfied, The ",,'iew has underlined the
panicular value of isotopie tTaceT lechniques in 'hiS a'pect of ecolo,icologj'
pro"ided care is exerciSoCd in interpreling data on the distribulion of Ihe
isotopic labels "'ithln a model ccosy'Stem
3.3.10 REFERE.!''''CES
AOAC (1981). S.,m/'Mi1U7l Pr<xndin&> Tn' 1'rol<>rob fw En>'if()Jthl~nO>1 F....ru1
I/o,........ nt of T<>.<i<anu, pp 1-330. Associ.,ion of OffICial Anal}tical O>emim
(AOAC), Wuhi"llon, DC (i" pre..)
SOILSYSTBIS
A}~".
,.,
R. S., ar>d W."COI. D W. (1976). Wale' qua~,) for aji:ricul'u," FAO ImB",,,,n
4M DNini1./I' Po~, .Y·o. 29. pp. ,-x;, .r><! 1_97. Rome:
Baker. D. E .• and 0..""1n. L. (1973). Ol<mlcal mon;'onn& 01 soil> 10< .n,·;,on",.n131
qu.Ii'y and anim.l.nd hum.n ... lIh, Ad,', AB,on" n.305-374
BiRlar. J W ..• nd G'..n...·ood. D. J. (1978), Spa,ial "ri,I>Ilil) 01 nI1n>J<n ,n "",1>. In
~ ..I.. n. D. R. and .~bcOon.Ud. J G. (Ed.). /o,"ro/I'n '" ,II< En",ro"""nl Vol, I.
Pr. 201-222. A<adem;c Prc". " ... York and Landon
B,,·oc.Smi'h. D. (1973). Pollu'ion oIlhe >Oil b) I'><a,') me13I', I. Ro."ol 50<.,,) ofA,,,.
m (SI99). IZo-l27,
BUller. G. C, (1978), E>l;mOl;OIl 01 <1<»<, and Inteara,.d d...... In BUlle,. G. C. (Ed.).
/'Tin6p1.. of EroIoxi«>/og-' , SCOPE 12. I'P. 91_lIZ. JOOn W;ley and Sons.
Olkhe.1<,. " ....' York. Bri
Toronlo
Cairn.. J. (1979). Hnza,d ~,·ol ,ion ...i,h microco<m', I", I.. f:n,;ron Sf""., 13.
9S_99,
CalJ<"b.nl., A. (1%8). Th. blp)riJ'lium h~,bicides. Adv P.., Conl'oI R.,.. 9.
127_235.
CEC (1972). Proc<~dins' of 4n In'mltTlional 5;·mpo.f,um on R.dii>-«oIov Appl,.d '"
,II< Prol«li"" of 11"" 4M~" En,'ironmml. Rome. 1971. Vol. r. I'P. I~XII .r><!
1-793, YoI, II, pp. 799~ I ~lT Comm'''lOn of lhe European Communilie, (CEq,
Lux.moou'a
CotlOnie. A .• and V.n de: M•• Ie, F. (1974). U. ril<iu•• de: pollution por r<mploi
;ncon,,61t de: ",,,;du' "'Pniqu,",. U Sol. Ipu,_u, bioc~,,,t1q~ IIOIU.-.I. Nan<)
l.l.r.....nda. P, W. A .• W;nl~rin",.m. F, P, W .. Rose, C. W ...nd p.r1a.&<. J Y
(1980). Luch,nl of , ""'bed <oJUlo • mod.1 lor peak CQ1I<en"Ol;OO d..pla<em.nl
Im'solion xi.. I. 169-1 H
Doubl<da~. G. P. (1974). Th< «c1ama'i"" of land al,~, coal m;n;ng. Oull""k A~ri<:" 8
(3).156-162.
Dugg.n. S.. and G>dd,ng>. J VI. (1978l. ,.... ,1\8 'o'i< ,ubs1>n<e' rO' protec'"," of ,he
~n,;ronm<n'- Sci. TOI..J Enllron .. '. 63_74.
Eb;oa. \\ and Schuphan. I. (1979). S'udi" "" tli< beh."i"", of <n,;ronmen,,1
ch.mic." in pl.n" ar><! "'il qu,nli"",.I)· ;n,·~"isal.d ;n <k>s<d <ult;"";nl 'r'lOm,
Ecosox En.."",. So!<'y. 3 (2l. 133-143.
Eh'lich. P. R .• Eh,lio;;h. A. H .••nd HoIdr<n. J. P. (1977), u.m:~nu-, Pop"",lion.
R.wurcn Em'iron"""'. W. H. Flttman. Co.. San F.. rocisco. IOSI pages,
EIIk;,. 1, 0, D .• Whc:<lock. J. y .•• nd Collon. D. E. (1981). Fac''''' .ff..,,;na >Oil
«';du<. 01 d;,ld"o•• ndowllan. ,..HOI. d'om.,hool' . •nd p)'01'•. JA=X
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FAO (19790), AI"""I,u",; To"'ard 2000, Do<:um<n, p1'C]>In:d lor ,I'>< ZOth S<s<.ion 01
!lI. ConI... ...,. of ,Ii< Food ,nd AgricullU" Organizalion 04' Iii< Unit.d 1'.lion.
(FAO). C 79,'H.I'P. I-x,,;;; 000 1-257. Rom~
FAO (19791», Ground",a,", pollullOn. FAO Ilngn,i"" ond V,n;"'g< Pope' Vo,31.
I'P, i-,,·; and 1_137. Rom<
FAQ IAEA (1979; 19800: 19Mb). t'OI~' "" Ol.mi<:al R."dues .nd Pollulioll
Program .... 04' ,h. Jo,n' Di"""" of Iii< l.l~rn ..ional A"""'" Er><'1) Ag.nq
(IAEA) and Iii< Food and Aa"""l1u .. Oq:.niz.tiQn of ,he 1;",1«1 N"",", (FAOJ
Clr~mo,p~.... 8 (lIil2). "4_N6,. (S/6). t'9_;-; 10,9 (11). N8_N9.
FAO·-'IAEA (198lX), A;roch.mical ,,";du<_bio,. ;nl~'Klion. in >oil .nd .quOlk
<Co>l"'''''· MEA P.-I Pro.:uding, S....... STI 1'1,;6 548, p!>. 1-305. v;."""'.
FAO'U"EP (1976). Impa<.1 """,;'orI08 04' 'l,","l'ural pe"iOdes, FAO. AGP;
1976 V~~. W. i_i, and I_lOll. Rome
fAQ,.Ul-iEP (1917), En,ironmtnlal ~h.mit:ab; cnt.ria fo' Ill< prolO,,;on of
non-hum.n bioi. in the conleXl of agricullure. for~",,·. fi,l'><ries and food Draft
mo""B,.ph dal«l 31 Decembe,. 1977. I'P. I-H 1. FAO. 1981 (;n I"~ss)
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TESTS TO PREDICT THE ENVIll,O:-;"E~"TAL BEHAVIOUR OF CHE"ICAl.S
Fe'1uson, J, (1939), Cbc:micaJ potentiob a. indie.. of ''''icit)·, Proc. Soc. Lottd. BIOi.
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An app",,"ch fo' comporlll;"e ...-«n;ol or the en'iron"",nlOl beh"iour of
chemical" EroltJ>:, EO"iron. ~/tty, J (2), 144-1~1.
Fried, 101 .. and B,oesharl, H. (I %7), Th~ Soil_Plom S}"Urn in R~I.'ion IQ lno'ganic
.'·w,i,ion. Aoad.emic Pr.... :-...... y",~ and London, H8 page'
Fn...!. M. I. (Ed.) (1977). C)'dllli of mine..1 nu',.,.n" in agricultural e""')~le"".
As""ucnJ>lmu. • (Ji2), i_.ii and I-H•.
Fri"'I, M. J, (1981), TWen') mod<l. fo, ,be: beh..iou, of nitrogen in ."il•.
Communica'ion to tile Xlhh Annual Mee.... of tbe European Socie'y of I'uolear
Metl>odo in AI"""I,"",. Aberdeen. UK. ~8 Sept. to 2 0c1. 19111
Fuhmnann, T, W.. aDd Lich'en"ein, E. P. (1978) R...... of ""I·bound
meth)'I-(''C}parath"", ",O'du•• and their uptakeb',' ea"hwOfm, and
plan". J,
Agrie. Foo4 Clttm, 26. 605-610.
G<rike. P., and Fioch.,. "" K. (1979). A "",rei,,,,,,, "udy of biodel"'dability
tlc:terminatiom ..ith ,..<iou. <:hemH:aJ. in ~ . t ..... &0_. En,';"",. ~ftry>
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Gilbert. P, A, (1979). Biotlc:.rodabilit)· and tbe e..imation of envi,onm.ntal
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nt...!ion., EcOI<>X. Envi,on. Sokry. 3 (2). 111-115
GI
N. R.. GIo... G. Land Renn'e. P. J. (1979). Eff<ct$ of acid p1cc;pit>hon
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Giopper. R. J. tlc:. and Smi ... H. (1974). Redam.,iQl\ of Ian<! lrom tile ..a an<! la~e. in
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Ham, 1, van dr,. Schmidt·BI«k. F., Kreuk. J. F dr. and Giin,be:r, K 0, (1981).
Conclu.ions and ,eoommenda,;on......Ilin. lrom tbe seoo.", wo.-Ubop
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IAEA (197~) Aqu.tio producri..-ity: isotopic tr.ce, ..d.d stud><, of
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IAEA (1976). Trace, manual on crops and ooib. IAEA, Tr<:h. Report Se~.
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ICRP (1960). Reoommendati"", 01 the International Comn",,",n on Rad,oI<>i'oal
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Kle,n, W.> and K""e. F. (1980), C..e ond compo'''i,e .,u<Ii.. "" .enobi<><ia in
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Kone, R.• and Winteti".h,m, F. P. W. (l980). l.->belled ,"b,"ra,e technique. a,
indicoton of all,r>chrmkal ,e>Kl",,_!liota inte ....ti,·") in ooiI and aquati<
«OOj'Sle,",. IAEA PONIPro<:rrdi,,!!, Serio" ST/'-PUB/518. PII' 23_33. Vien"".
Komt>c:'II. H, (1979). ROJaI Co",miuiM "" £O";ro"""'Olal Poil","'o. W, i_X an<!
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Ko.-te. F.. F,.ita.. D.. Ge)er. H., K",n, w., Krau., A G.. and L-ah,n,"tio, E. (1978}.
Eooto.koIogl< pro/il. aruJ)m. Clttmo>~re, 7 (I), 79_102
Kurihara, K. (1978). 11H: uO< of industrial and muni-cipol .... st.. o. orpDi< fertilize,
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l.l.t<:aIf, R. L (197~). A I.borat"'}, model «»s}"em I", <"o'alua"nl the ehrmical and
F1flCh,
Boo~
oa,
'"
SOil SYSTB'S
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1'>;.1",,,. D, R .. W"rengo. p, l.. .nd E1,U"'. J. W, (19801», '-1""em."t of ",trate ," ,he
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collection ou ........... 1.¥.1s .nd .",'i,onm."t,,1 .ff«t> of • ..Me
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."d pb)sical '1.""" (..,..te be... I>DM, etc.) in CllJIlIda. R.port. of ,be Associa,.
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192
n:srs m
PREDlCf THE
E."VIRO~ \1E'TAt
pollu'",n of '.aler IAEA Pond P"Xudmgs
VieM3
llEHAV10l,;R OF OIBlICAl..S
~fU"
STI/PUBI3M. pp. 63-76,
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